Punch press stripper



Nov. 23, 1948. 'r. T. CRANDALL ,PUNCH PRESS STRIPPER Filed Nov. 22, 19462 SheecsSheet 1 INVENTOR. I THE/QU/V TOQA/VDALL w mk 'r. 11. CRANDALLPUNCH PRESS STRIPPER Nov. 23, 1948.

Filed Nov. 22, 1946 2 Sheets-Sheet 2 INVENTOR. v THERO/V 7' (RANDALLATTD RN EYB Patented Nov. 23, 1948 I TED STAT E S I PATENT OFFICEPUNGH,:=PRESS STRIPPER Theron 1T. Crandall, Cano'galPark, Calif,

Application November 22, 1946, Serial No. 711,783

punch of the press to strip the work from the punch, and which isespecially designed for use with quick-acting machines of the pneumaticor other power operated "and upright type.

As is well known, after the reciprocatingpunch on its working strokepasses through the work, 7

as a metal sheet, and into the die, frequently on the return stroke ofthe punch the work binds or sticks to the punch .andis lifted from thedie. To remedy this objectionable condition time and labor are requiredin removing the work from I the punch and .in re-assemb'ling "the partsfor subsequent operations.

The primary object :of .my invention is the -pro vision of a strippingmechanism for co iaction with the reciprocating punch, that isautomatically actuated by the punch on its working stroke to hold downthe work "on the die, and springoperated for following, after-a delayinterval, the punch on its return or retracting stroke. The strippingmechanism includes a minimum number of parts that may "with facility bemanufactured at low cost of production, and assembled; and installedwith standard types of punching machines with conveniencefitoinsure -a:mechanism' that is simple in operation, reliable in the performance ofits functions, and effective in use.

The invention consists in certain novel combinations and arrangements ofparts as will hereinafter be described and more specifically set forthin my appended claim.

In the accompanying drawings I have illustrated one complete example ofthe physical embodiment of my invention wherein the parts are combinedand arranged in accord with one mode I have devised for the practicalapplication of the principles of the invention. It will be understoodhowever, that changes and alterations are contemplated and may be madein these exemplifying drawings and mechanical structures, with in thescope of my claim, without departing from the principles of theinvention.

Figure 1 is a view in side elevation showing so much of a punchingmachine as is necessary to illustrate the installation of the strippingmechanism, which is here shown in held down position with the work onthe die; and Figure 2 is a front face view of the equipment shown inFig. 1.

Figure 3 is a horizontal sectional view as at line 3-3 of Fig. 2; andFigure 4 is a similar view at line 44 of Fig. 2.

Figure 5 is a view similar to Fig. 1 but showing the punch uplifted,together with the stripper mechanism, in order to give access to thework for adjustment of the work on the die.

4 IClaim. (01164-410) In order that the general arrangement andutllityof parts may readily be understood I have shown .in the assemblydrawings a portion of the machine frame F, including the die holder H,upon which the die D is mounted; and a metal sheet on which the patternhas previously been laid out by a template, is designated as the work W,andsupportedonthedie for punching according to the pattern.

The punch shaft S, which is power operated to reciprocate vertically inbearings of the frame F directly above the die is fashioned with a punchP and pilot point or nib N, and as indicated in the drawings, the lowerend of the shaft S forms an annular shoulder A.

.In carrying out my invention the reciprocating shaft S is equipped witha vertically adjustable actuating lug or abutment in the form of acollar or ring I that is mounted on the shaft, and fixed in set positionby means ofia set screw or set bolt 2 threaded through the collaragainst the shaft. This rigidly mountedactuating lug I travels with theshaft to automatically trip a holding-down .or latch device for thestripper at the end of its upward or return stroke and release thestripper as indicated by the position of parts of the mechanism .in Fig.5.

Thestripping mechanism includes a stripper or holding down arm 3 havinga forked or bifur cated free end 4 that encompasses the punch P, and.this arm is pivoted or hinged at 5 to the lower end of a sectional,vertically adjustable bracket composed of a lower section B to which thestripper arm is connected by a helical spring I that tends to elevatethe forked end of the stripper arm and cause it to follow the punch onits upward or return stroke. In addition to the lower section 6, thissectional bracket includes a fixed section 9 and these sections areadjustably connected by means of a pair of slots 1, l in the lowersection and pairs of clamp bolts 8, 8 mounted on the fixed section, inorder that the bracket may with facility be adapted to the dimensions ofa punching press. The fixed section 9 of the bracket is fashioned withan angular flange 10 that is firmly secured in proper position by boltsI l which attach it to the frame F.

On the working stroke of the punch the stripper arm 3 is pressed downagainst tension of spring I by contact of the shoulder A with the forkedend 4 of the arm 3, and as the punch P passes through the work W andinto, die D the stripper is held down, by arm I9 and stop lug 23, in theposition of Fig. 1, until it is tripped on the return or upper stroke-ofthe punch.

For releasing the holding down device of the stripper on the up strokeof the punch, the lug or collar l on the shaft S of the punch co-actswith an oscillatible trip lever having a short arm l2 and a rightangular longer arm l3 and pivoted at M on a bracket arm l5 which isrigidly mounted, as by welding, on the attaching flange ill of theadjustable bracket 6-9.

The bracket arm I5 is provided with bearing holes, as 16 for the pivotpin 14 in order to permit accurate adjustment in the assembly of parts,and a cotter pin as H is employed to retain the pivot pin againstdisplacement.

The actuating arm 12 of the trip lever is located above the lug orcollar I and in the pathof movement of the reciprocating collar or lug,so that on its upstroke the lug will strike arm 12 and thereby swing thedepending arm l3 of the lever inwardly toward the punch, The lower endit of the arm i3 is bifurcated to straddle an obliquely disposed lockinglink or spring latch l9 that is instrumental in holding down thestripper 34 on the work as the punch is being withdrawn therefrom. Thebifurcated end I8 of the trip lever co-acts with a cross-pin 20 of thelatch I9 to form a loose pin and slot connection between these partsthat permits relative movement of the parts without actuallydisconnecting them.

The latch arm or locking link 19 is pivoted at 2! on the upper face ofthe stripper, and an aux- I iliary spring 22 forms a spring hinge thattends to swing the link l9 away from the punch and constantly in contactwith the pin 20; and when free to act, spring 122 swings the link orlatch l9 into position under an abutment 23 welded on bracket section 9.

With the parts in position of Fig. 5 ready access is had to adjust thework W on the die for a punching operation, and as the punch descends,it pushes the stripper 34 downward. v

The lug or collar I withdraws its support from the arm E2 of the triplever leaving the lever dangling freely, and as the stripper is presseddown, the latch 18 under force of spring 22 is swung on its pivotsending its upper free end against the section 9 of the supporting,bracket and under the abutment 23 of the bracket; and the stripper isthus held down on the work W by the link 19 in engagement with its stopor abutment 23, as indicated in Fig. 1.

On the upstroke of the punch, the stripper holds down the work until thecollar or lug l strikes the short arm I2 of the trip lever, and bypositive action of the trip leveragainst pin 20 the link, l9, which isspring-held, is withdrawn from under the stop or abutment 23. Now theextended spring 1, by contraction, lifts the stripper to position ofFig. 5 to clear the work and die and permit adjustment of the work, andthe stripper mechanism is again in position for operation under asucceeding working stroke of the punch.

The pin 20 rides or slides at all times in close contact with thedepending arm or bifurcated end l8 of the arm l3 of the trip lever, andthe springs 1 and 22 constantly tend to hold the pin against the arm.

Having thus fully described my invention, what I claim as new and desireto secure by Letters Patent is:

The combination with a reciprocating punch having an actuating lug, anda fixed frame, of an adjustable bracket and means-for fixing it on theframe, a stripper pivoted on the bracket and having a forked free endengaging the punch, a lifting spring connecting the stripper with thebracket, a spring-pressed link pivoted on the stripper and an'abutmenton the frame for engagement by the free end of the spring-pressed link,an L-shaped trip lever having one arm in the path of said lug andpivoted on the frame, a second lever arm straddling the link, and across pin on the link in constant engagement with the straddling arm.

THERON T. CRANDALL.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 655,074 Graves July 31, 19001,933,465 Woodburn Oct. 31, 1933

